3 things you can literally learn in your sleep

 If someone suggested you play music or light a scented candle while you slept to better remember what you learned earlier in the day, you'd probably laugh.
But while you might not be able exchange a night of studying for playing some jazz while you snooze, there are some surprising skills you can strengthen overnight — some simply by playing a specific tune or by infusing your bedroom with a distinct smell.
Scientists are still a bit fuzzy on the specifics, but they've found some powerful examples of the practice working in the real world.
They know, for instance, that people can better remember the location of an object if overnight they listen to the tune they heard when they put it there. Similarly, someone learning a foreign language can boost her skills by playing the sounds of newly-learned foreign words while she sleeps.
While the next step may be applying these techniques to try to sharpen memory and learning more broadly, here are a few examples of the specific skills scientists have found can be honed while you are fast asleep.
Learn Foreign Words
In a recent experiment, scientists had native German speakers begin learning Dutch, starting with some basic vocabulary. Then, they played the sound of a few of those Dutch words to some of the German speakers while they slept, without telling the German speakers what they were doing. Compared to those who had no sound playing overnight, the group who heard words in their sleep were better able to identify and translate them later.
The most convincing part? It only worked for the specific words that were played.
To make sure the findings were tied to sleep — and not just the result of people hearing the words — they had another group listen to the words while they walked. The walkers didn't recall the words nearly as well as the sleepers.
Why? The likeliest answer points to our sleeping brains, whose activity slows down at specific periods throughout the night. During these slow-motion periods, our brain is hard at work moving our short-term memories from temporary storage to our prefrontal cortex, where they are recorded for the long-term.
When the researchers looked at the brain activity of their German-speaking volunteers on an EEG, they noticed that those who listened to the foreign words overnight had more slow-wave brain activity throughout the night.
More slow-waves, the scientists reasoned, translated into better recall of the new words.
Hone Musical Skills
The findings aren't just limited to the sound of words. Music can do the trick as well.
Researchers recently had a group of people learn to play guitar melodies using a technique borrowed from the video game Guitar Hero. Then, all of the volunteers got to nap.
Unbeknownst to them, a selection of the sleeping participants were played the same melody they had just learned. After their slumber, the volunteers played the tune again. Those who heard it while napping — even though they had no memory of doing so — played the melody far better than those who didn't.
Keep Specific Memories From Fading
We forget a surprising amount of information, especially the dates and descriptions we deem insignificant. Our brains use a special tagging system to differentiate between important experiences and inconsequential ones. Those the brain tags "important" get sent straight to our long-term memory hard drive. The "unimportant" memories, on the other hand, are left in short-term limbo where they get washed away by new memories.
What if that tagging system went awry, however, and the memories your brain labeled insignificant were the ones you wanted to keep?
Scientists recently found that people who listened to a sound they associated with a memory — even an inconsequential one — were better able to hold on to that memory.
First, they had a group of volunteers place icons on a computer screen in a specific location. The computer was programmed to play a specific sound when each object was placed. Placing a cat icon played a meowing noise; placing a bell icon prompted a ringing sound. Then, they let participants nap. While they dozed, the scientists played the sounds of some of the icons (again, the volunteers didn't know this was happening).
Here's the weird part: The people who listened to the sounds — any of the sounds — were better able to recall all of the objects. In other words, one sound triggered multiple memories.
The findings parallel earlier research where scientists used smell instead of sound: A 2007 study found that people given whiffs of a rose while they learned something remembered it better later when they inhaled the same smell while asleep.